Diets rich in cruciferous vegetables such as broccoli are associated with a reduced risk of cancer. Animal studies have identified sulforaphane, an isothiocyanate, as the ingredient in broccoli responsible for protection against cancer. This is a randomized, double-blind, placebo controlled inpatient evaluation of the safety and tolerance of broccoli sprout isothiocyanates or glucosinolates (the inert form of isothiocyanates stored in intact plants). Four escalating dose levels of broccoli sprout preparations (25, 100 micromol glucosinolate; 25, 100 micromol isothiocyanate) will be studied in a sequential fashion, each level in a cohort of four healthy volunteers (3 active, 1 placebo). There is a five day washout, seven day dosing, and final seven day washout period. Subjects are maintained throughout the study on a diet free of glucosinolates and isothiocyanates. Doses are given every eight hours for a total of 21 doses. Blood is collected before, during and after dosing, and sent for a battery of hematology and chemistry studies. Urine for assay of isothiocyanates and metabolites is collected continuously throughout the entire study, in 8 hr intervals.